Zigzag ginning theory and discharge of cotton seeds
There is a theory that attaches great importance to the discharge of cotton seeds in the working box. It is believed that in order to improve the productivity of the sawtooth gin, the residence time of cotton seeds in the working box should first be reduced. In addition, the amount of flower feeding and cottonseed discharge must be increased to maintain a balance under high yield.
As shown in the picture As shown in 8-22, the fibers on the single-particle cotton are gradually rolled off; when the single-particle cotton first contacts the saw teeth, there are relatively more fibers that can be caught by the saw teeth because there are a large number of fibers on the cotton. As the number of times of padding and stripping increases, there are fewer and fewer long fibers on the cotton, and there are fewer and fewer fibers of single-grained cotton that can be caught by the saw teeth. That is, there are fewer and fewer opportunities for single-grained cotton to be rolled and peeled. In addition, the curve of the rolling and peeling progress of a single particle of cotton and its residence time in the working box takes the abscissa as the asymptote. That is, the long fibers on the single particle of cotton can be rolled only when the single particle of cotton stays in the working box for an infinite time. Finished peeling. In order to ensure efficient ginning productivity, it is very necessary to properly control the cotton wool rate and discharge the cotton in a timely manner.
(1) The discharge process of cotton seeds
In the working box, when the cotton seeds are relaxed to the D area, they almost move to the saw teeth along the inclined direction of the cotton seeds comb. Cotton with fibers can be taken away by the saw teeth because the saw teeth directly hook the fibers on it, or the fibers on it are adhered to the single particles of cotton hooked by the saw teeth. Cotton with slight fiber or only short velvet is difficult to be hooked by the saw teeth and loses the conditions for adhesion with other cotton, so it can only be squeezed into the saw blade gap. In this way, at the cotton comb, the saw teeth are sorted according to the amount of fiber in the cotton. The cotton seeds that are not selected by the saw teeth and fall into the gap of the saw blade are divided into two situations:
1. The cotton seeds are in direct contact with the side of the saw blade
The cotton seeds that are in direct contact with the side of the saw blade are in direct contact with the saw blade. Friction force P is generated between the blades, and the direction of P is along the tangent direction of the saw blade at the contact point. The friction between the side of the saw blade and the cotton seeds is converted into the impulse on the cotton seeds, as shown in Figure 8-23. Under the condition that the speed of the saw blade roller remains unchanged, the magnitude of the impulse depends on the contact between the cotton and the saw blade. When cotton seeds contain more fibers, the friction impulse is larger, and vice versa.
Let someone The mass of cotton falling into the gap of the saw blade is m. The speed at which it moves along the cotton comb toward the saw teeth is v0. The speed after contacting the side of the saw blade is v. The distance between the cotton and the saw blade is The time of indirect contact is t, which can be obtained from the momentum theorem:
mv=mv0+Pt
That is, the cotton is combed and sawed The momentum after contact between the sheet sides is the composite of Pt and mv0. mv0 is almost a constant. The more fibers there are in the cotton, the greater the influence of mv on Pt. The farther the cotton is thrown, finally landing on the ginning rib far away from the cotton comb. The flatter upper part. On the contrary, the less fiber the cotton seed contains, the less the mv is affected by Pt, and the closer the cotton seed is thrown, and finally falls on the steeper part of the lower part of the ginning rib that is closer to the cotton seed comb.
2. The cotton seeds are not in direct contact with the side of the saw blade
The part of the cotton seeds that is not in direct contact may be pulled by the nearby cotton that is hooked by the saw teeth, and the length of time the cotton seeds are pulled by the single-particle cotton depends on Depends on the degree of connection between cotton seeds and single-particle cotton. The more fibers there are on the cotton, the closer the connection between it and the single-grain cotton, and the longer the cotton is under the traction effect. When the cotton is separated from the traction of the single-grain cotton, it finally falls on the flatter place on the upper part of the ginning rib. On the contrary, the fewer fibers on the cotton seeds, the shorter the time the cotton seeds are pulled by the single-grain cotton, and finally fall at the steeper lower part of the ginning rib.
The cotton seeds falling on the ginned ribs are affected by three forces (because the surface of the ginned ribs is very smooth, the friction between the cotton seeds and the ginned ribs can be ignored), namely the gravity of the cotton seeds themselves, The supporting force of the ginning ribs on the cotton and the friction of the side of the saw blade on the cotton. The gravity of the cotton seed itself makes the cotton seed slide down along the surface of the ginned rib; the friction force of the saw blade on the cotton seed causes the cotton seed to move upward along the surface of the ginned rib with the rotation of the saw blade. When the cotton seeds fall on the flat upper part of the ginned ribs, the tangential component of the cotton seeds’ gravity on the surface of the ginned ribs is very small, and the friction force of the saw blade on the cotton seeds plays a dominant role, causing the cotton seeds to move along the surface of the ginned ribs. Move and return to the sub-roll. The cotton seeds falling on the steeper part of the lower part of the ginning rib are greatly affected by gravity, slide down along the surface of the ginning rib, leave the middle box and are discharged out of the machine. In this way, the cotton that falls into the gap of the saw blade is sorted by the saw blade again, and only the cotton with long fibers is discharged out of the machine.
The above description, that is, the “second sorting theory” is a relatively representative statement. There is also a theory that when the cotton roll comes to the cotton comb and encounters a rapidly rotating saw blade roller, because the surface linear speed of the saw blade roller is much greater than the surface linear speed of the cotton roll, it is torn apart by the saw teeth from the outside to the inside. The cotton in the cotton roll is discharged along the crack channel under the action of inertial centrifugal force and self-weight.
(2) Factors affecting the discharge of cotton seeds
If the gross rate of discharged cotton seeds is too large, it will increase the loss of clothing; if the gross rate of discharged cotton seeds is too small, it will affect the quality of cotton lint and ginning and stripping. velvet raw materialTherefore, the cotton wool rate should be controlled within an appropriate range. The national standard “Cotton Fine Staple Cotton”
(GB1103-1999) stipulates that the cotton lint rate is: when sorting grade 1 and grade 2 cotton, not more than 0.4%; when sorting grade 3 to 5 cotton, not more than 0.4%. greater than 0.6%.
Whether the cotton seed discharge is smooth or not has a great influence on the cotton seed hair rate and the cotton seed uniformity. When the cotton seed discharge is not smooth and the cotton feeding speed is above the middle gear, the cotton seed roll will be very tight. When the cotton feeding speed is at the high gear, the cotton seed roll will stop spinning. If the cotton seed is discharged smoothly and the cotton feeding speed is above the middle gear, the cotton seed roll will not be tight; when the cotton feeding speed is at the high gear, the cotton seed roll will keep rotating. Therefore, it is particularly important to ensure smooth discharge of cotton seeds. It is mainly affected by the following factors:
1. Working box geometry
A working box with a reasonable shape can create better conditions for the cotton that has been rolled to be discharged from the working box in a timely manner.
2. The tightness of the cotton roll
The cotton is easily discharged when the cotton roll is loose. Because the sub-cotton rolls are loose, the holding effect between the cotton seeds and the sub-cotton rolls is weak, and the cotton seeds are easily separated from the sub-cotton rolls and discharged smoothly. Especially when the cotton roll comes into contact with the saw teeth at the cotton comb, due to the sudden acceleration of the single particle cotton relaxation speed, a crack is torn open in the cotton roll by the saw teeth, so that the cotton can be discharged smoothly. When the sub-cotton rolls are tight, it is difficult to form a crack channel when the sub-cotton rolls encounter saw teeth. Moreover, the cohesive effect between the cotton seeds and the sub-cotton rolls is strong, which can easily lead to poor cotton discharge. In order to discharge the cotton seeds smoothly, the curvature radius of the working box and the plate can be adjusted to a large value and the cotton roll density to a small value, which is conducive to the discharge of cotton seeds.
3. Adjustment of the cotton comb
Adjusting the inclination of the cotton comb is crucial for the smoothness of the row and for controlling the lint rate of the discharged cotton. When the cotton comb is lifted upward, the local density of the cotton roll at the cotton comb increases, and the cotton is less likely to be discharged; conversely, when the cotton comb is tilted downward, the cotton is easily discharged. Therefore, the degree of adjustment and control of the cotton comb has a great relationship with the position and structure of the cotton comb. In addition to the inclination adjustment, the cotton comb of the new sawtooth gin can also be adjusted forward and backward to adjust the gap between the cotton comb and the gin rib row.
This two-way adjustable cotton comb strengthens and improves the regulating effect of the cotton comb, and is more conducive to the discharge of cotton.
4. The size of the platoon channel
The platoon channel is the channel between the embossed rib row and the shell rib row. During ginning, the channel is divided into many “well”-shaped channels in the length direction by the saw blade roller. The size of the pavilion is determined by the length and width of the “well”-shaped channel. The length and width of the “well”-shaped channel are determined by the gap between the embossed rib row and the shell rib row and the saw blade distance. When other conditions are the same, if the gap between the embossed rib row and the shell rib row is large, the cotton seeds are easily ejected to the steeper lower part of the ribs, and the cotton seeds are easily discharged; conversely, the cotton seeds are easily ejected to the flat upper part of the ribs. Cotton seeds are not easily discharged. The embossed rib row and the shell rib row can be adjusted within a small range, but it should be ensured that the embossed ribs do not collide with the saw blade roller spacer, and the height of the saw blade extending beyond the shell ribs should be ensured. Under the same conditions, if the saw blade pitch is large, the cotton seeds are easily discharged; on the contrary, the cotton seeds are not easy to be discharged, so the reduction of the saw blade pitch is limited.
5. Saw blade spacing and sawtooth status
When the saw blade spacing is large, the number of cotton seeds falling between the two saw blades is larger, and the number of cotton seeds in contact with the side of the saw blade is relatively small, that is, there is no There are many cotton seeds affected by the impulse. It is relatively simple for most of the cotton seeds to overcome the coupling force of the cotton rolls and the friction of the saw blade due to the action of gravity, and the cotton seeds are easily discharged. If the pitch of the saw blade is small, there will be more cotton in contact with the saw blade and it will be difficult for the cotton to be discharged.
The jaggedness is not sharp, and too much incompleteness will severely affect the hooks of the zigzal cotton in cotton comb, so that the hair rate of the cotton is a large hair rate, and the loss of clothes is severe.
6. The inclination of the embossed ribs
When the embossed ribs are adjusted in the vertical direction, the lower part of the row is expanded, and the flatter part of the upper rib tends to be inclined, which enhances the gravity of the cotton on the row. The function is to make the rows smooth. When the embossed ribs are adjusted in the opposite direction, it will affect the row.
(3) The leisure trajectory of cotton seeds in the working box
In order to discharge the cotton seeds that meet the requirements of hair rate out of the machine in time, in addition to adopting reasonable process parameters and improving operating methods on the existing machine models In addition, another method is to innovate the existing platoon mechanism.
AAASVSGHRUTO
